Volvo: 1990 740 Turbo AC, systemmatic, power antenna

Question
Picked up this car as a project with my son.
No air, compressor won't come on, not a fuse.
I know it's a process. I have the book, no details.
What I need is a systemmatic troubleshooting process to isolate the problem. If I send it out it will probably cost as much as I paid for the car if not more.
Many other issues also, power antenna, sun roof etc etc..
but at a later time.

Thanks in Advance for your help.

Answer
John.
Ok not a fuse, so have you tested with a test light? Start at the drier and see if you have power at either wire that goes to the low pressure switch. If you have power at both wires follow the wire to the compressor and see if you have power there. No power both sides of the low pressure switch wire; no power from the dash control head. No power from only one side of the switch; defective switch or low enough on freon to not allow the compressor to come on. Power all the way to the compressor check the ground wire for the compressor.
This test is with the engine running and the A/C switched on. At all times being aware that their are moving parts.